Answer:
the 5th month
Step-by-step explanation:
Triax=
1st month $50 phone+ $40fee = $90 first month
2nd month= $90+$40=$130
3rd month= $170 (I think you caught on tp the add $40 each month)
4th month= $210
5th month=$250
CellUR=
1st month = $50
2nd month = $50+$50=$100
3rd month = $150(I think you caught on tp the add $50 each month)
4th month= $200
5th month=$250